An incubator is widely used as a device to keep and culture samples used for culturing and testing microbes or cells. The incubator has various instruments to maintain environmental condition such as temperature, humidity, oxygen concentration and carbon dioxide concentration in an incubation chamber in which the samples are stored. In culturing, the incubation chamber is maintained in high humidity state equal to or more than 90% of humidity at temperature 37° C. In order to maintain the specified culture environment, the incubator has atmosphere measuring means such as a temperature-humidity sensor, a carbon dioxide sensor, and an oxygen concentration sensor thereinside, and besides a control device to keep the inside in a specified environment from datum detected by the atmosphere measuring means.
When atmospheric unwanted bacteria, cultured cells or microbes remain in the incubation chamber, so-called contamination occurs in next culture because the unwanted bacteria and so on are mixed with a culture medium, therefore bringing bad influences to the cells and the microbes under culture. Accordingly, an operation called sterilization is required to remove bacteria other than the purpose before starting culture.
For the conventional incubator, is adopted a sterilization method to irradiate ultraviolet rays or a sterilization method called dry heat sterilization to kill the unwanted bacteria by keeping inside temperature equal to or more than 130° C. However, there are problems in these methods, for example, the sterilization is insufficient or it takes long time to start the next culture from the expiration of the sterilization. Therefore, gaseous sterilization, in which sterilizing is performed the incubation chamber by an impregnated sterilization gas such as hydrogen peroxide gas and ozone, has been recently widespread, and an incubator with a gaseous sterilization function has become common.